The present disclosure relates to novel compounds which exhibit inhibition of fibroblast growth factor receptor tyrosine kinases (FGFRs), in particular FGFR1, FGFR2, FGFR3 and/or FGFR4, pharmaceutical compositions comprising the compounds, to processes for making the compounds, and the use of the compounds in therapy. More particularly, it relates to 2-aryl- and 2-heteroaryl-substituted 2-pyridazin-3(2H)-one compounds useful in the treatment or prevention of diseases which can be treated with an FGFR inhibitor, including diseases mediated by FGFR tyrosine kinases.
Fibroblast growth factors (FGFs) and their receptors (FGFRs) regulate a wide range of physiologic cellular processes, such as embryonic development, differentiation, proliferation, survival, migration, and angiogenesis.
The FGF family comprises 18 secreted ligands (FGFs) which are readily sequestered to the extracellular matrix by heparin sulfate proteoglycans (HPSGs). For signal propagation, FGFs are released from the extracellular matrix by proteases or specific FGF-binding proteins, with the liberated FGFs subsequently binding to a cell surface FGF-receptor (FGFR) in a ternary complex consisting of FGF, FGFR and HPSG (Beenken, A., Nat. Rev. Drug Discov. 2009; 8:235-253).
There are five FGFRs, of which four (FGFRs 1-4) are highly conserved single-pass transmembrane tyrosine kinase receptors (Eswarakumar, V. P., Cytokine Growth Factor Rev., 2005; 16:139-149). The binding of an FGF to an FGFR leads to receptor dimerization and transphosphorylation of tyrosine kinase domains (Dieci, M. V., et al., Cancer Discov. 2013; 3:264-279; Korc, N., and Friesel, R. E., Curr. Cancer Drug Targets 2009; 5:639-651). Activation of downstream signaling occurs via the intracellular receptor substrate FGFR substrate 2 (FRS2) and phospholipase Cγ (PLC-γ), leading to subsequent upregulation of RAS/mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K)/AKT signaling pathways. Other pathways can be activated, including STAT-dependent signaling (Turner, N., Grose, R., Nat. Ref. Cancer 2010; 10:116-129; Brooks, N. S., et al., Clin Cancer Res. 2012; 18:1855-1862; Dienstmann, R., et al., Ann. Oncol. 2014; 25:552-563).
FGFR signaling components are frequently altered in human cancer, and several preclinical models have provided compelling evidence for the oncogenic potential of aberrant FGFR signaling in carcinogenesis, thereby validating FGFR signaling as an attractive target for cancer treatment.
The mechanisms by which FGFR signaling is dysregulated and drive cancer are better understood in recent years, and include activating mutations, FGFR gene amplification, chromosomal translocations, autocrine and paracrine signaling, and altered FGFR splicing.